With increasing popularity of high resolution digital processing devices such as High Definition Television (“HDTV”) and high quality imaging processing devices, a fast and accurate mass storage device has been increasingly in demand. Magnetic storage media such as magnetic tape has continued to be an efficient medium for data storage for the high resolution digital processing devices such as computers and HDTV. To enhance data storage and retrieval performance in a tape recording, it is critical to position the transverse head at a right location over the magnetic tape. In digital tape recorders, voltage peaks arising from pre-recorded, slanted magnetic stripes on tape are typically used to determine transverse head position based on peak-to-peak time intervals.
To enhance the head position with respect to the tape, a conventional approach is to use multiple stripes that can be detected by a magnetic head. FIG. 1 shows a conventional technique that includes two stripes 101 and 102. Stripe 101 is configured to slant at a positive angle with respect to the tape 100 and stripe 102 is slanted at a negative angle with respect to the tape 100. Stripes 101 and 102 are separated by a distance down the tape 100. When the head position 103 is near the top of the stripes 101-102, the servo signals or pulses 105 caused by the stripes 101-102 will occur wherein the distance (or time) between the pulses or peaks is t1. When the head position 104 is near the bottom of the stripe pair, the pulses or servo signals 106 will occur wherein the distance (or time) between the pulses is t2. It should be noted that t2 is greater than t1 wherein the difference in distance or time indicates the location of the head position. For example, if the detection of stripes 101-102 is around t1, it indicates the head is at the head position 103, while if the detection of stripes 101-102 is around t2, it indicates the head is at the head position 104.
Given the knowledge of the tape speed, the instantaneous transverse location of the head may be determined by measuring the time interval between the servo stripe pulses detected by the head. The head can then be adjusted to position as desired by measuring a succession of stripe pairs continuously. To make the measurements, the servo signals or pulses 105 or 106 are delivered to a detection logic that reports the time of occurrence of each peak. A problem associated with this conventional approach is that the servo signals or pulses derived from the stripes are difficult to detect. Another problem associated with this approach is that the conventional detection scheme is susceptive to timing error due to noise on the servo signals. Yet another problem is that when a sampled-data system is employed, the accuracy of peak time location is limited by the sampling rate, since the peak of interest may fall between samples at an unknown time.
Accordingly, there is a need in the art to improve the noise immunity and the detection of the servo signals.